This product is no longer available.

Note: The DGPS kit requires the use of the Oncore VP GPS engine. Motorola discontinued the Oncore VP in August of 1999. TAPR is no longer able to supply Oncore VP units for this kit. We suggest you contact Synergy Syetsm (Gina) for any Oncore VP units they might have available. While new units are no longer available, surplus and refurbished units can be found.

Differential GPS Reference Station Interface on left
Example of Oncore attached to DGPS Interface on right

For example, a Radio Amateur installation would use a 2-meter transmitter
and TNC.; Using the 2-meter frequency of 144.39 MHz, the new APRS
frequency, APRS trackers can take advantage of DGPS accuracies (see performance
below).; No special equipment is needed by remote users.; Corrections
are received using a 2-meter (mobile or handheld) receiver and TNC.;
The output of the TNC is connected to a DGPS "ready" receiver.

Commercial users can connect the DGPS Interface board to commercial
data radios.; The responsibility of using the correct frequencies
is up to the user.

Possible uses include:

Search and Rescue

APRS Trackers

Parades

Marathons

Balloon Tracking

Research and Development

Vehicle Location in a metropolitan areas

Anything that requires increased GPS accuracy

Setup of the DGPS Reference Station is easy.; The output baud rate
and the Station ID is selectable via jumpers.; The latitude, longitude,
and altitude of the reference location and the rate at which corrections
will be transmitted are programmed via software commands.; The Reference
Station then operates without any further intervention.

Performance

Using Stan Huntting's, KW7KW, SA Watch program, you can see the difference DGPS has over civil GPS.;
The following GPS receivers were held stationary and received differential
corrections from the TAPR DGPS Reference Station. Differential corrections
were transmitted on 145.79 MHz (the previous APRS frequency) and two plots
were made for each receiver.; The first plot without differential
corrections and the second with.

Zero Baseline Tests

The Zero Baseline test connects the TAPR DGPS Reference Station to a remote
GPS receiver under test using the same antenna.; Both receivers connect
to the same antenna via a 2-way DC isolated L-band power splitter.

Zero Baseline Test

The Zero Baseline test connects the TAPR DGPS Reference Station to a remote
GPS receiver under test using the same antenna. Both receivers connect
to the same antenna via a 2-way DC isolated L-band power splitter.
The plots below were made using a Oncore VP as the remote DGPS receiver.
The reference coordinates were 30:46:58.965N 81:40:30.830W. The RTCM
output of the Reference Station was connected directly to the Oncore VP
(i.e., no radio link).

Zero Baseline test were also done with the following GPS receivers as
remote receivers:

The below plot positions were collected for 10 hours 17 minutes.
The RTCM output of the Reference Station was at a rate of one message every
1 second. SAWatch calculated the 95th percentile at 3 meters.
The scale of the outer ring is 15 meters.

The below plot positions were collected for 11 hours. The
RTCM output of the Reference Station was at a rate of one message every
5 seconds. SAWatch calculated the 95th percentile at 4
meters. The scale of the outer ring is 15 meters.

The below plot positions were collected for 11 hours 19 minutes.
The RTCM output of the Reference Station was at a rate of one message every
10 seconds. SAWatch calculated the 95th percentile at 5
meters. The scale of the outer ring is 15 meters.

The below plot positions were collected for 10 hours 35 minutes.
The RTCM output of the Reference Station was at a rate of one message every
15 seconds. SAWatch calculated the 95th percentile at 8
meters. The scale of the outer ring is 15 meters.

The below plot positions were collected for 10 hours .
The RTCM output of the Reference Station was at a rate of one message every
20 seconds. SAWatch calculated the 95th percentile at 8
meters. The scale of the outer ring is 15 meters.

The below plot positions were collected for 12 hours 32 minutes.
The RTCM output of the Reference Station was at a rate of one message every
30 seconds. SAWatch calculated the 95th percentile at 14
meters. The scale of the outer ring is 15 meters.

Garmin 45 Zero Baseline Test

The below plot positions were collected for 8 hours 24 minutes. The
RTCM output of the Reference Station was at a rate of one message every
1 second. SAWatch calculated the 95th percentile at 14 meters.
The scale of the outer ring is 30 meters.

Garmin GPS-20 Zero Baseline Test

The below plot positions were collected for 6 hours. The RTCM output
of the Reference Station was at a rate of one message every 1 second.
SAWatch calculated the 95th percentile at 18 meters. The scale of
the outer ring is 30 meters.